Better handling of online/offline behavior, socket shutdown (#1593)

* Online/offline: Always stop timer, don't connect if closed

* Sockets: Send our own close event faster, shutdown only on close

Seems that we were too-aggressively disconnecting from all socket
events. Also, we should be able to send our own close event a lot
faster with no ill effects.

* Catch-up libtextsecure changes

js/background.js

@@ -185,6 +185,10 @@
             disconnectTimer = null;
             return;
         }
+        if (disconnectTimer) {
+            clearTimeout(disconnectTimer);
+            disconnectTimer = null;
+        }
 
         connect();
     }